The way DH is used typically for encryption (ECIES) or in TLS doesn’t give you authentication. But you can get authentication from DH alone, without PSK or PKI. See https://neilmadden.blog/2021/04/08/from-kems-to-protocols/ for some details on the security properties of various types of DH.
I meant that some data still needs to be distributed securely, just it's the sender's public key rather than a PSK. I recon "pre-shared data" was not the best choice of words...
